But I am wondering if there is a way of solving this with a config setting or possibly some plugin?

In short, the problem is the following: When performing a case-insensitive search for "ABC", Sublime also returns results for abc, aBc etc. Just as it should. But when searching for characters such as ÅÄÖ, á, ñ etc. the search is case sensitive. So when searching for "å", strings with "Å" are not found. But they should be.